BINARY IONIC COMPOUNDS Naming and Writing formulas

Ionic Compounds: Formed by combining a cation with an anion. Held together by an ionic bond The attractive force between ions of opposite charge. Crystal lattice structure: Repeating ordered pattern of positive and negative ions Represented by a formula unit Displays the lowest ratio of ions in the crystal Example: CaCl 2

Examples of crystal structures

Forming Cations and anions Cation: Positively charged ion formed by an atom losing one or more electrons; usually a metal Example: calcium loses two electron. Anion: Negatively charged ion formed by an atom gaining one or more electrons; usually a nonmetal. Example: chlorine gains one electron.

Learning Check: Determine the number of electrons either lost or gained when forming the following ions: 1. S Na Al Br N -3 Are the ions listed above cations or anions?

Naming Binary ionic compounds Binary = 2 elements (metal w/ one nonmetal) Step #1: Name the cation first. Step #2: Name the anion using the –ide ending. Example: 1) BaF 2 Barium fluoride *subscript does not effect the naming

Learning Check 1. Name the following ionic compounds: a. NaO b. MgI 2 c. CaBr 2 d. Li 2 S Answers: a. Sodium oxide b. Magnesium iodide c. Calcium bromide d. Lithium sulfide

WRITING FORMULAS Binary Ionic Formulas

How do we know the Ion’s Charge? Group 1 = +1 Group 2 = +2 Group 13 metals = +3 (Al, Ga and In) Group 15 Nonmetals = -3 (N & P) Group 16 Nonmetals = -2 Group 17 = -1 For Groups and Sn & Pb: Roman Numerals equal positive charge* Example: Iron (III) = Fe +3 Copper (II) = Cu +2

Goal = Balance charges The sum of the positive charges must equal the sum of the negative charges. zero Overall charge equals zero! Example: Why is calcium chloride’s formula CaCl 2 not just CaCl? Ca +2 Cl -1 You need 2(-1) chloride ions to balance the 1(+2) calcium ion.

Writing formulas: Criss-cross Method Write formulas for ions with charges. Cation first, anion second. Criss-Cross charges making them subscripts Reduce if necessary- Always need lowest ratio of ions Example: Magnesium fluoride

More examples Lithium oxide Calcium sulfide Aluminum selenide Iron (III) bromide

Review - Learning Check Write the formulas for the following binary ionic compounds: 1. Manganese (III) oxide 2. Strontium sulfide 3. Calcium iodide 4. Chromium (VI) fluoride

Learning Check Answers 1. Manganese (III) oxide Mn 2 O 3 2. Strontium sulfide SrS 3. Calcium iodide CaI 2 4. Chromium (VI) fluoride CrF 6

NAMING IONIC COMPOUNDS WITH TRANSITION METALS Groups and Sn & Pb

Naming Compounds with Transition Metals A roman numeral must appear in name when dealing with transition metals and Sn & Pb. Work backwards from formula to determine charge on cation.  Exceptions: Zn +2, Ag +, Cd +2 Example: NiCl 2

Practice Problems: Name the following compounds 1. Cr 2 O 3 2. MnS 3. ZnCl 2 4. FeI 3 1. Chromium (III) oxide 2. Manganese (II) sulfide 3. Zinc chloride 4. Iron (III) iodide